Thermostat apparatus



Feb. 23, 1932.

J. PICARD ETAL 1,846,752

THERMOSTAT APPARATUS Filed Jan. 50, 1928 '6 :i la.' $4! a 20 I 1a F f2 lQ/ .1 RL l i@ f Vd A "IG-'P' ur 'T- E /L/'71r\- l, :1' Lvrnfdro': *a 6]6 l' cfges .Zz'aar nl nlref Zurnairo Patentedv Feb. 23, 1932 UNITEDSTATES PATENT OFFICE THERMOSTAT APPARATUS Application med January 30,1928, Serial No. 250,641, and in Belgium February 2, 1927.

The present invention relates to a detecting i apparatus of thethermostat type adapted to control the operation of an indicating or analarm device, should any part of the said apparatus be subjected to anabnormal rise of temperature, whether this rise is too rapid or thetemperature attains a determined degree, showing in either case anabnormal condition to which attention must be paid. The said detectingapparatus essentially comprises a band of a readily expansi'ble substance which subtends a double spring device preferably consisting of twostrips formin'g an elliptical set or combination which vN5 will beflattened when the middle band is elongated by its heating which isindependent of the elliptical set.

The elongation of the middle band will atten the elliptical set, andthis motion is uti- L0 lized to control the indicating or alarm devicecoacting with the apparatus.

To provide for the lengthening of the middle band independently of thestrips of the elliptical part, during an abnormal rise of temperature,which is either too high or too rapid, the strips of the said ellipticalset are so constructed that in the first instance they will heat up moreslowly than the vmiddle band, for example by covering them with aheat-protecting covering or by giving them a higher caloric capacity,and in the second instance they consist of a substance having a very lowcoeiiicient of expansion, such as invar metal.

In our complete apparatus we thus employ two different detectingelements correspqnding to the two types described.

In the case of an electric indicating plant operating upon constantcurrent, the elliptical part of each detector is preferably secured to asupport at the middle part of one of its strips, and at the middle partof the other strip is mounted a small spring plate or an electricContact piece coacting 5 with an adjustable screw mounted in the saidsupport; said plate and screw forming part of an electric circuit whichmay be common to both detectors of the same apparatus.

In the accompanying drawing:

Figures 1 and 2 are, respectively, a vertlcal section and a plan view ofthe improved apparatus or device, andv Fig. 3 is an end view.

The apparatus herein represented comprises a base 4 upon which aremounted by 55 means of screws 5 and 6 two suitable detecting elementsdisposed side by side in spaced parallel relation, one of which consistso a strip 7 which is secured at its center to the said base by the screw6. To the ends of the o0' strip 7 are secured by rivets 8, or bysoldering, the ends of an upper strip 11, similar to the strip 7.

Between the ends of the strips 7 and 11 are secured the respective endsof a band 12 consisting of a substance having a high coetlicient ofexpansion, preferably interposed between heat-insulating disks 9 and 10.

The band 12 subtends the strips 7 and 11', and it is given a length suchthatl it will hold 7o the strips in curved position, despite theirnatural tendency to become flattened.

The strips 7 and 11 are so constructed that they will heat up lessrapidly than the band 12, and this may be obtained by covering the 'I5`strips with a heat-protecting layer, indicated at 20 on Figs. 2 and 8,or by giving Vto them a heating capacity greater than that of the band12, i. e., by making them thicker.

The other detecting element of the appa- 8 ratus is secured by the screw5 to the support 4, and it has the same disposition as the iirst, exceptthat the two strips 7 and 11'l of this element consist of a substance,such as invar metal, having a very low expansion coeficient. The disks 9and 10 are no longer necessary in this case.

The middle part of the upper strip of each element comprises a resilientmetal plate 14 90 coacting with an adjustable contact screw 15 mountedin a metal frame 16 secured to the base 4.

In the usual case in which the strips of the two elements consist ofmetal, the ends of the electric wires are connected to the respectivescrews 5 and 6 which are insulated from the frame 16, so thatthe circuitis closed through the said strips, the plates 14, the

screws 15 and the bar 16. 100

at the same time as the strips 7 and 11 whose heat insulation, or greatcaloriiic capacity, does not prevent a slow heating, equal to that ofthe band, so that the deliection of the elliptical set will notappreciably vary, and the device will not operate.

Should the temperature rise in an abnormally rapid manner, for instance2 per minute, the second detecting element will not operate as long asthe temperature for which it is regulated is not attained; but in thefirst detector, .the band 12 will expand without a4 correspondingexpansion of the strips 7a and 11, which heat up more slowly, and thusthe deliection of the elliptical set diminishes and the upper strip llceases to make contact with the screw 15, so that the circuit is brokenand the alarm set off.

If the temperature rises to the point corresponding to the adjustment ofthe second detector, but too slowly to operate the iirst detector, as inthe case of a smouldering fire,

the second detector, whose strips 7a and 11a consist of invar metal andwill not expand, thus breaks the circuit due to the suliicient expansionof its strip 12.

The operating temperatures may he regulated by the screws 15 which areheld in the proper position for instance by the small set-screws 19.This adjustment might also be effected by varying the length of thestrips, or their curvature, or the length of the band 12. Theseoperations may4 be effected by pressing the ends or by sliding themunder the rivets 8, or by like means.

The advantages obtained by the said apparatus are obvious. It operatesunder all conditions in a rapid and precise manner, due to the lowcaloritic capacity of itsV parts, and chiefly of the band 12, and itwill also resume the normal position of vits own accord when the severalconditions which produced its distortion have ceased to act.

This last property allows it to automatically indicate a lire whichstarts again after an incomplete extinguishing.

The band 12 is subjected to tension stress, and the effort is exertedupon it in the direction of its length, so that the band may be'madevery thin, thus oierin a great sensitiveness and also agreat di erencein heat capacity as compared with the strips 7 and 11, or 7a and 11a.This sensitiveness is increased from the fact that the variation in thedeliection of the elliptical part of an element is twice the variationof the deflection of each strip.

Due to the expansion of its parts, the sensitiveness of the element(which operates by the sudden rise of temperature) will slightlydiminish as the temperature rises, and will approach the operating pointof the other element. This sensitiveness, which can be automaticallyvaried, `will thus depend inversely upon the temperature.

well as non-rusting, and it will not lose its adjustment. It forms acompact and rigid whole, and can be readily manufactured in standardsizes on a large scale. Its several parts are readily removable.

Obviously, the said invention is not limited to the example hereindescribed, and without departing from the' spirit of the invention, wemay employ only one detecting element per apparatus, or the detectorsmay be connected in separate circuits.

The construction of a detecting element may be simplified; for instance,one of the strips 7 may be eliminated, but in this case thesensitiveness will evidently be reduced by one' half. Y

The detecting elements can be used in plants employing electricsignalling, or mechanical or compressed air signalling, or other meansfor this purpose.

lfVe may employ the detecting element to observe the value of anelectric current, by sending the whole or a part of the current into theband 12 itself.

The said apparatus can be used for protection against tire or to show anabnormal rise of temperature in any suitable place or apparatus, or thelike.

We claim:

1. Thermostatic apparatus, comprising a skeleton, vertical frameembodying connected top and bottom members; a pair of oppositely-bow'ed,expansible spring strips disposed one above the other within the frame;a metal band expansible independently of and differently from the springstrips and having its opposite ends interposed between the strip endsand connected with the same; an adjustable contact screw mounted 'in thetop member of the frame to coact with the upper spring strip; and ascrew securing the lower spring strip to the bottom frame member; thetwo screws and spring strips being included in a normally-closedelectric circuit which is broken by the separation of the contact screwand upper strip consequent upon the different expansion of the' stripsand bandY The apparatus is practically ireproof, yassuch as chemicalbaths, lfurnaces,

Luana i ient metal plate which is mounted centrally upon that strip andwith which the contact screw directly contacts.

3. Apparatus accordin to claim 1, in which the top member of t e frame'has a set screwl movably mounted in it to enga e the Contact screw andretain it in adjus position.

4. Thermostatic apparatus, com rising a skeleton; vertical frame; a pairo thermostatic devices mounted therein side by side and embodyin each, apair of oppositelybowed, eXpansl le spring strips disposed one above theoth-er, and a metal band expansible independently of and dierenty fromsaid strips and having its opposite en s interposed between andconnected to the strip ends; the strips of one device heating lessrapidly than the band thereof, and the strips o the other device beingmade of a substance having a very low coefficient of expansion; coactlngcontact means on the frame top and the upper strip of each device; andmeans securing the lower strip of each device to the bottoni of theframe; said contact means and securing means andthe spring strips of thetwo devices being included in a normall closed electric circuit which isbroken by t e' separation of the .contact means of either deviceconsequent upon the expansion of the band thereof when an abnormaltemperature rise occurs.

5. A device for detecting abnormal temperature rises, comprising twooppositelybowed strips, and a band subtending the l strips and havingits ends interposed between ends; said strips and. band being the strimade o materials having the same expansibility, the stri s having agreater thickness than the ban and insulating disks interposed betweenthe ends of the strips and those of the band.

6. A device for detecting sudden temperature changes, comprising twooppositelybowed, expansible strips, and a band subtending the strips andhaving its ends interosed between t ose of said strips; said band ingthinner than the strips and made of a material having the samecoeiiicient of expansion as vthe strips, so that the heat ca aciy olfthe strips is greater than that o the In testimony whereof we affix' oursignatures.

JACQUES PICARD. ANDR TOURNADRE.

